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Oguzhan Yildiz

Gulhane School of Medicine, Turkey

Title: Pharmacology of arterial grafts for coronary artery bypass surgery

Biography

Oguzhan YILDIZ, MD, has completed his PhD at the age of 29 years from Hacettepe University and postdoctoral studies from University of California, Irvine. He is professor of Medical Pharmacology at Gulhane Faculty of Medicine. He has published more than 60 papers in reputed journals and has been serving as an editorial board member of repute. 

Abstract

Interest has increased in the use of arterial conduits for CABG significantly in most major cardiac surgery centers around the world, because the number of patients receiving arterial grafts and our knowledge about the biologic characteristics of arterial grafts have increased. In addition, more advanced clinical protocols for the use of grafts have been developed and midterm results with alternative arterial grafts are encouraging. The internal mammary artery (IMA) has been shown to have greater long-term patency for coronary artery bypass grafting when compared with the saphenous vein graft. Because of the superior long-term results of the IMA, other arterial grafts which have recently been advocated include the radial artery (RA), the gastroepiploic artery (GEA), the inferior epigastric artery (IEA), the splenic artery, the subscapular artery, the inferior mesenteric artery, the descending branch of lateral femoral circumflex artery, the intercostal artery and the ulnar artery. One ofthe  various  manifestations  clinically  observed  among  these  arterial  grafts  is  a  different tendency to develop spasm during surgical dissection and during the perioperative period which could be the cause of perioperative morbidity and mortalitiy. For example, there are reports of vasoactive drugs altering IMA graft flow. Moreover, there is accumulating evidence that blood flow in arterial grafts is insufficient in some circumstances. Many vasoconstrictors  (spasmogens)  may  cause  arterial  grafts  spasm.  Accordingly,  antispastic therapy  is  important  in  the  development  of  arterial  grafts  and  the  nature  of  constrictor substances that cause arterial graft spasm needs to be determined. In recent years, the problem of  graft  spasm  has  become  more  frequent  with  the  increasing  use  of  new  arterial  grafts. Therefore, it is essential for surgeons to understand the causes of vascular graft spasm, to improve  patency  rates  and  to  use  the  optimal  vasodilator  in  the  most  appropriate  way  to counteract vasospasm. Surgeons have studied graft pharmacology by measuring the effects of vasodilators on blood flow through arterial grafts before they were attached to the heart. Pharmacologists have also joined the study of graft pharmacology by evaluating endothelial and smooth muscle function  of  bypass  grafts  using  their  standard  in  vitro  method,  the  isolated  vessel  ring preparation in the organ bath. However, results from these in vitro studies need to be carefully extrapolated to the clinical situations, where the conditions of the arterial grafts are complicated. Even so, the organ bath method can provide very useful information about the effects of vasoactive substances in the arterial grafts. Several vasodilators have been tested and various antispastic methods have been suggested to prevent graft spasm; including papaverine, phenoxybenzamine, calcium antagonists and nitrates etc. Choice of a pharmacological agent to overcome the vasospasm encountered in the arterial grafts must be on the basis of pharmacological studies. Accordingly, current state of knowledge based on experiments to study the pharmacological effect of a number of vasoconstrictor and vasodilator substances and the practical application of this knowledge will be summarized.